System and method for conserving energy resources through storage and delivery of renewable energy

ABSTRACT

A system for encouraging the use of renewable energy sources and suitable for the conservation of energy resources through the efficient management of energy storage and delivery includes connections to a power source, an energy storage subsystem, and a power grid. The system includes a power routing subsystem coupled to the source and grid, and adapted to operate in a bypass mode, in which energy is transferred from the source to the grid. The system includes a conversion subsystem coupled to the routing and storage subsystems, and switchable in substantially real-time between a storage mode, in which energy is transferred from the routing to the storage subsystem, and a generation mode, in which energy is transferred from the storage to the routing subsystem for delivery to the grid. The system also includes a controller for directing the modes based at least in part on a market factor.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/372,238, filed on Feb. 13, 2012, and entitled “System and Method forConserving Energy Resources through Storage and Delivery of RenewableEnergy,” which claims priority to U.S. Provisional Patent ApplicationSer. No. 61/588,461, filed Jan. 19, 2012, the entireties of which arehereby incorporated by reference.

TECHNICAL FIELD

The invention relates generally to a system and method for managingenergy storage and delivery, and more specifically to a system andmethod for encouraging the use of renewable energy sources and theconservation of non-renewable resources through the efficient managementof energy storage and delivery.

BACKGROUND INFORMATION

Existing power generation methods typically fall into specific groups,namely: (1) baseload power delivery, which comes from generators thathave technologies that enable them to economically sign contracts tosell power 24 hours a day, seven days a week, such as nuclear, coal,hydro, biomass, and some combined cycle gas; (2) intermediate powerdelivery, which is power delivered approximately 16 hours a day, either5 or 7 days a week, mainly from combined cycle gas plants; (3) peakerpower delivery, which is delivery of power for about eight hours a day,5 days a week, and is roughly coincident with peak load, and which ismainly from simple and combined cycle gas plants and some diesel plants;and (4) intermittent sources which cannot be scheduled, such as wind andsolar. In addition to these power generation services, there are alsomarkets for power quality services, such as frequency regulation up,frequency regulation down, capacity, black start, ramp-rate control,spinning reserve, and non-spinning reserve.

Current technologies that are directed toward renewable energy sourcesmainly transform intermittent resources such as wave, wind and solarinto intermittent power. Many of these renewable resources are difficultto predict and schedule. The extensive development of global wind-powerhas given rise to efforts to address the challenges of intermittentenergy sources with respect to generating electricity for power grids.Many of these efforts involve the development of means to conditionintermittent electric power sources that supply a grid, so as tominimize or counteract the disturbances that would otherwise affect thegrid in undesirable ways. Other efforts involve developing energystorage means that can act to the benefit of wind farms and otherintermittent sources of renewable energy. Energy storage means provide abenefit for intermittent sources by harvesting into storage so-calledexcess capacity during periods when electricity may be generated inexcess of the current electricity demand. The electricity that might begenerated, for example, by a wind farm during periods when wind energyexceeds the grid's energy consumption, might be assigned a low ornegative price, or the wind farm curtailed (disconnected) from supplyingenergy to the grid. Similarly, in a grid significantly powered byintermittent sources, grid energy demand might go unmet during periodswhen energy demand is greater than the available wind energy.

One important form of power conditioning that may facilitate increaseduse of wind, and similarly intermittent renewable energy sources, is thedevelopment of means to transform wind energy from being an intermittentpower resource to being a fully dispatchable power resource able tooffer firm power contracts. Firm power contracts are contracts todeliver a specified amount of energy to a specified point during aspecified time period, and require the seller to pay penalties if theycannot meet the terms of the contracts. Firm contracts command a pricepremium to intermittent contracts in most markets, and are thereforevaluable. Efforts to transform intermittent wind into firm power haveheretofore depended upon forecasting future wind velocities (forpurposes of selling into the day-ahead market), and coordinatingoperation of the wind-power generation with other remotely sitedintermittent power sources, and/or coordination with more-constant powersources, such as hydro, whose power flow rate can be varied up or downto compensate for higher or lower flow rate from a wind farm, and/orcoordination with thermal generators such as simple cycle gas plants anddiesel plants that can ramp up or down in response to the real-timeoutput of wind farms. Such coordination efforts do not transformintermittent wind energy into firm power, but they do help intermittentwind to be integrated into the grid. Power generators must increasinglyparticipate in competitive markets established to govern electric powergeneration/sale/trading. Therefore, the development of wind (and otherintermittent renewable energy sources) in the United States (and otherparts of the world) is severely impeded by its lower market value.

A means to enhance the economic value of wind and other intermittentrenewable energy sources in the competitive deregulated power tradingmarket is vital to increasing deployment of renewable energy generation.Increasing the economic value of wind is perhaps the most importantlong-range determinative factor for renewable energy growth in theUnited States. Given a federal commitment to maintain and developcompetitive markets for electric power generation/sale/trading, theself-evident competitive drivers for use of renewable energy areenhanced price and reduced cost. Governmental and academic studies ofthe future prospects for renewable energy explicitly recognize thesignificance of price and cost factors in the current day competitivemarket.

To date, various efforts to provide energy storage to wind farms havenot transformed wind-generated electric power into firm power within thepricing framework of the grid, even though the addition of storage hasameliorated to some extent the intermittent nature of wind-power.Implementations of compressed air energy storage (CAES), pumped hydrostorage, battery, flywheel, thermal storage, and other storage meanshave been limited in this regard by technology. Existing technology hasnot demonstrated the ability to produce electric power outputs that arevalued by the competitive grid as premium power.

Accordingly, there exists a need to provide systems and methods thattransform intermittent power into firm power, such that the use ofrenewable energy sources is further encouraged.

SUMMARY OF THE INVENTION

The present invention achieves firm electric power by combining anintermittent power source, such as wind, with a storage means such asCAES. The present invention is designed to enable flexible, responsivegeneration of power well-suited to win premium prices as inputs to theelectric power grid—such as base power, following power, intermediatepower, peaking power, supplemental reserves, replacement reserves,spinning reserves, non-spinning reserves, black start, and frequencyregulation—in a manner that is not interrupted by lack of wind or othertypical intermittent factors.

The flexible nature of the system enables a controlled transformationbetween compressed gas energy and electrical power—in either direction(reversibly, subject to efficiency losses)—thus enabling a method of(economically) purchasing and selling electric power from/to the grid,at full market price rather than at diminished intermittent wind-powerprices. The system further enables a power trading strategy based on oneor more factors of current price, average past prices, future predictedprices, current state of intermittent power source, predicted futurestates of such intermittent power source, current state of capacity ofenergy storage in the CAES system, current state of utilization ofelectric motor-generators, current capacity of wind turbines or otherintermittent power engines, system costs, transaction costs, powersupply and demand, and other factors having an effect on energy pricing,storage and distribution.

Accordingly, in one aspect of the invention, a system for managingenergy storage and delivery includes a connection to a power source, aconnection to an energy storage subsystem, a connection to a power grid,a power routing subsystem, a conversion subsystem, and a controlsubsystem. The power routing subsystem is coupled to the power sourceand the power grid, and is adapted to operate in a bypass mode, in whichenergy is transferred from the power source to the power grid. Theconversion subsystem is coupled to the power routing subsystem and thestorage subsystem, and is switchable in substantially real-time betweena storage mode, in which energy is transferred from the power routingsubsystem to the storage subsystem, and a generation mode, in whichenergy is transferred from the storage subsystem to the power routingsubsystem for delivery to the power grid. The control subsystem directs,based at least in part on a market factor, the conversion subsystemand/or the power routing subsystem to operate in a specific mode.

The power source may be an intermittent power source, which can be anyof wind energy, solar energy, wave energy, tidal energy, falling water,hydro energy, biomass energy, and geothermal energy. Moreover, theintermittent power source may produce electrical power.

The storage subsystem can be of a medium such as fluidic storage,mechanical storage, kinetic storage, electrical storage, electrochemicalstorage, and thermal storage, and may include a storage volume which canbe any of a pressure vessel, a subterranean cavern, a well, a flywheel,a battery, piping, a bladder, a hydrostatically pressure-compensatedcontainer, a lake, a pond, a liquid storage vessel, a water retentionstructure, and a capacitor.

In one embodiment, the system is adapted to store energy as compressedgas. The conversion system may further include a motor/generator, ahydraulic pump/motor, a hydraulic actuator, and a compressor/expanderconnected in one of series or parallel.

The controller may direct the modes of operation by comparing the marketfactor to a threshold. The mode direction may further be based at leastin part on the available capacity of the storage subsystem.

In one embodiment, the controller can switch the conversion subsystem tooperate in the storage mode when the market factor is less than thethreshold and there exists available storage capacity, and in somecases, can switch the conversion subsystem when the market factor isless than the threshold by at least a predetermined margin. Thepredetermined margin may be decreased when the available capacity isgreater than a predetermined value, and may be increased when theavailable capacity is less than a predetermined value.

In another embodiment, the controller directs the system to operate inat least one of the generation mode and the bypass mode when the marketfactor is greater than the threshold, and in some cases, can direct thesystem to operate in a mode when the market factor is greater than thethreshold by at least a predetermined margin. The predetermined marginmay be increased when the available capacity is greater than apredetermined value, and may be decreased when the available capacity isless than a predetermined value.

In yet another embodiment, the controller directs the mode of operationbased at least in part on environmental conditions. The environmentalconditions may be local environmental conditions and/or remoteenvironmental conditions, as well as present conditions and/or projectedconditions. The environmental conditions may include wind speed, winddirection, air temperature, air pressure, humidity, precipitation, cloudcover, season, length of daylight, tidal status, storage temperature,storage pressure, storage time, and day/night temperature differential.

The threshold can be, for example, a present supply, a future supply, apresent demand, a future demand, an average market price, or a currentmarket price. In some cases, the market factor may be a market price ofelectricity, a present market price of electricity, a future marketprice of electricity, a trending price of electricity, a supply ofelectricity, or a demand of electricity.

In one embodiment, the controller further includes a power deliveryalgorithm. The power delivery algorithm may be adapted to fulfill along-duration power service simultaneously with at least one ancillarypower service. The power delivery algorithm may be adapted to fulfill apower service such as baseload, intermediate, peaking, load following,frequency regulation, spinning reserve, non-spinning reserve, blackstart, reactive power control, load source on demand response, and/orramp-rate control. In some embodiments, the power delivery algorithm isadapted to fulfill the power service by simultaneously operating thesystem in the storage mode and the bypass mode. In other embodiments,the power delivery algorithm is adapted to fulfill the power service bysimultaneously operating the system in the generation mode and thebypass mode.

In further embodiments, the system includes a trading subsystem forinitiating at least one of a purchase of electricity, an offer topurchase electricity, a sale of electricity, and an offer to sellelectricity. The trading subsystem may be adapted to fulfill a powerservice by buying electricity at a market price, and selling electricityat a contract price.

In another aspect of the invention, a method for managing energy storageand delivery includes the steps of connecting to a power source,connecting to an energy storage subsystem, connecting to a power grid,routing at least some energy produced by the power source to the powergrid, and automatically switching in substantially real-time betweenstoring energy by transferring energy from at least one of the powersource and the power grid to the storage subsystem, and generatingenergy by transferring energy from the storage subsystem to the powergrid. The switching may be based at least in part on a market factor.

The power source may be an intermittent power source, which can be anyof wind energy, wave energy, solar energy, tidal energy, falling water,hydro energy, biomass energy, and geothermal energy. Moreover, theintermittent power source may produce electrical power.

The storage subsystem can be of a medium such as fluidic storage,mechanical storage, kinetic storage, electrical storage, electrochemicalstorage, and thermal storage, and may include a storage volume which canbe any of a pressure vessel, a subterranean cavern, a well, a flywheel,a battery, piping, a bladder, a hydrostatically pressure-compensatedcontainer, a lake, a pond, a liquid storage vessel, a water retentionstructure, and a capacitor.

In one embodiment, the routing step is performed automatically. In oneembodiment, the storing step includes compressing gas.

The routing and switching steps may be based on a comparison of themarket factor to a threshold. The routing and switching steps may befurther based at least in part on an available capacity of the storagesubsystem.

In one embodiment, the switching step further includes switching tostoring energy when the market factor is less than the threshold andthere exists available storage capacity, and in some cases, includesswitching to storing energy when the market factor is less than thethreshold by at least a predetermined margin. The predetermined marginmay be decreased when the available capacity is greater than apredetermined value, and may be increased when the available capacity isless than a predetermined value.

In another embodiment, the switching step further includes switching togenerating energy when the market factor is greater than the threshold,and in some cases, includes switching to generating energy when themarket factor is greater than the threshold by at least a predeterminedmargin. The predetermined margin may be increased when the availablecapacity is greater than a predetermined value, and may be decreasedwhen the available capacity is less than a predetermined value.

In yet another embodiment, the routing and switching steps are furtherbased at least in part on environmental conditions. The environmentalconditions may be local environmental conditions and/or remoteenvironmental conditions, as well as present conditions and/or projectedconditions. The environmental conditions may include wind speed, winddirection, air temperature, air pressure, humidity, precipitation, cloudcover, season, length of daylight, tidal status, storage temperature,storage time, storage pressure, and day/night temperature differential.

The threshold can be, for example, a present supply, a future supply, apresent demand, a future demand, an average market price, or a currentmarket price. In some cases, the market factor may be a market price ofelectricity, a present market price of electricity, a future marketprice of electricity, a trending price of electricity, a supply ofelectricity, or a demand of electricity.

In one embodiment, the method further includes the step of deliveringpower to the grid to fulfill a power service. The delivering step mayfurther include delivering power to the grid to fulfill a long-durationpower service simultaneously with at least one ancillary power service.The power service may be baseload, intermediate, peaking, loadfollowing, frequency regulation, spinning reserve, non-spinning reserve,black start, reactive power control, load source on demand response,and/or ramp-rate control. In some embodiments, the delivering stepfurther includes delivering power to the grid to fulfill the powerservice by simultaneously storing energy and routing energy. In otherembodiments, the delivering step further includes delivering power tothe grid to fulfill the power service by simultaneously generatingenergy and routing energy.

In further embodiments, the method includes the step of trading energyby initiating at least one of a purchase of electricity, an offer topurchase electricity, a sale of electricity, and an offer to sellelectricity. The trading step may include fulfilling a power service bybuying electricity at a market price, and selling electricity at acontract price.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a system diagram illustrating by example an energy storage anddelivery system according to an embodiment of the invention.

FIG. 2 is a table illustrating by example the technical parametersassociated with an embodiment of the invention.

FIG. 3A is a table illustrating by example a baseline energy balancecase according to an embodiment of the invention.

FIG. 3B is a table illustrating by example a high price/available supplycase according to an embodiment of the invention.

FIG. 3C is a table illustrating by example a low price/availablecapacity case according to an embodiment of the invention.

FIG. 4A is a chart illustrating by example a baseline energy market caseaccording to an embodiment of the invention.

FIG. 4B is a chart illustrating by example a low capacity storage caseaccording to an embodiment of the invention.

FIG. 4C is a chart illustrating by example a high capacity storage caseaccording to an embodiment of the invention.

FIG. 5 is a table illustrating by example fixed band trading parametersassociated with an embodiment of the invention.

FIG. 6 is a model diagram illustrating by example an optimization modelaccording to an embodiment of the invention.

FIG. 7 is a diagram illustrating by example the inputs and outputs to adispatch algorithm according to an embodiment of the invention.

FIG. 8 is a graph illustrating by example a visual representation of adispatch algorithm output according to an embodiment of the invention.

FIG. 9 is a table illustrating by example predictive trading parametersassociated with an embodiment of the invention.

FIG. 10 is a block diagram illustrating by example a computer systemaccording to an embodiment of the invention.

DETAILED DESCRIPTION

As background, FIG. 1 is an illustration of an embodiment of an energystorage and delivery system 100 in which an energy conversion subsystem(e.g., a compressor/expander device) may be used to both store energyand release energy that has previously been stored.

An exemplary gas compression and expansion system usable for practicingthe present inventive subject matter is described in U.S. patentapplication Ser. No. 12/977,724, filed Dec. 23, 2010 (now U.S. PatentPublication No. 2011/0258996 A1), the entirety of which is herebyincorporated by reference.

A system such as that shown in FIG. 1 and described herein is availablefrom General Compression, of Newton, Massachusetts, under the nameGeneral Compression Advanced Energy Storage (GCAESTM). The embodiment ofthe invention described herein incorporates the GCAES system. A personhaving skill in the art should appreciate, however, that the inventionmay utilize any energy conversion system suitable to practice theinventive subject matter herein described. The system may be capable oftransferring and converting electric power or any other form of powerwith which the system may be compatible, such as hydraulic power.

As shown in FIG. 1, a power source 102 (e.g., a wind farm including aplurality of wind turbines) may be used to harvest and convert wind orother types of energy to electric power for delivery to a power routingsubsystem 110 and conversion subsystem 112. It is to be appreciated thatthe system 100 may be used with electric sources other than wind farms,such as, for example, with the electric power grid, or solar powersources. In some embodiments, the power source 102 is collocated withthe GCAES system. It should be noted, however, that the power source 102may be distant from the GCAES system, with power generated by the powersource 102 being directed to the GCAES system via a power grid or othermeans of transmission. The power routing subsystem 110 directselectrical power from the power source 102 to the power grid 124 orconversion subsystem 112, as well as between the power grid 124 and theconversion subsystem 112.

The conversion subsystem 112 converts the input electrical power fromthe wind turbines or other sources into compressed gas, which can beexpanded by the conversion subsystem 112 at a later time period toaccess the energy previously stored. The conversion subsystem 112 mayinclude an interconnected (in series or parallel) motor/generator,hydraulic pump/motor, hydraulic actuator and compressor/expander toassist in the energy conversion process. At a subsequent time, forexample, when there is a relatively high demand for power on the powergrid, or when power prices are high, compressed gas may be communicatedfrom the storage subsystem 122 and expanded through acompressor/expander device in the conversion subsystem 112. Expansion ofthe compressed gas drives a generator to produce electric power fordelivery to the power grid 124. In some embodiments, multiple conversionsystems may operate in parallel to allow the GCAES system to convertlarger amounts of energy over fixed periods of time.

The GCAES system is able to interface with very large storagecontainers, such as subterranean caverns, which are able to hold energysufficient to supply hundreds of hours of power at commercially viablelevels. Having the ability to access 5 to 300 hours of power fromstorage allows the formation of long-term power contracts (e.g., a 20-to 25-year baseload contract) which are otherwise not possible whensupplying power with intermittent power sources in conjunction withsignificantly smaller storage tanks. Further, a GCAES unit is able toswitch between generation/idle/storage modes on the order ofmilliseconds to seconds (compared to minutes, hours, or even days withother types of energy generation systems), which allows a GCAES energyprovider to provide ancillary services such as frequency regulation at amoment's notice. Further, in some instances, the ancillary services maybe provided simultaneously with the fulfillment of a long-duration powerservice or other short-term or ancillary services. If necessary, one ormore individual GCAES units may be activated or deactivated to meetcurrent demand, to trade energy on a power market, or to store energyfor later use.

Conversely, some types of energy generation systems, such as gas plants,if operating optimally, are able to go up and down numerous times over aday, although this will result in additional wear on the plants'turbines. Such activity may be intended with peaker plants, which mustoperate at a higher rate during peak power usage hours. Power plantturbines, however, are substantially worn by frequent cycling; that is,there is deterioration caused by the turbine fins growing and shrinkingfrom heating and cooling during spin-up and spin-down. It is thereforenecessary to provide sufficient time between cycling to avoid damagethat may occur from rapid changes in temperature.

Other examples of less flexible energy producers include coal plants,which can take several days to shut down and turn back on, and nuclearplants, which can shut down quickly, but may require days to come backonline. The common thread of cycling limitation among these power plantsis all related to thermal limitations. The GCAES system, however, doesnot encounter such thermal issues to any similar degree, and can cyclemany times over a single day.

The above-described abilities of the system as well as the independencefrom many of the fuel pricing, regulatory, environmental, and globalevent risks that accompany other types of power generation (e.g., coal,nuclear) allow GCAES plants to enter into contracts to providelong-duration power services, such as long-term peaking contracts (e.g.,sell power 8 hours a day, 5 days a week), intermediate contracts (e.g.,sell power at all hours except off-peak hours (5 to 7 days a week, 16hours)), and baseload contracts (e.g., sell power 7 days a week, 24hours a day). The GCAES system also allows for a long-duration loadfollowing contract, wherein the supplying of power may vary greatlydepending on an energy consumer's needs.

The capabilities of a GCAES plant go beyond its unique ability toutilize intermittent and steady energy sources combined with GCAES unitsto provide long-duration power such as baseload, capacity, orintermediate power. For instance, the segmentation of the plant systemsprovides flexibility in supplying power via a plurality of subsystems,each capable of rapid-time response to a power need, independent of theother subsystems. To satisfy these various needs, GCAES plants mayinclude, among other subsystems, multiple GCAES energy conversion unitsthat may function independently of each other. Combined with a massivescale-capacity energy storage subsystem and the ability to draw powerfrom various energy sources, the GCAES system joins high-speed responsewith longer duration of response compared to other energy storage andgeneration systems (e.g., flywheels, supercapacitors, and the like).

Notably, a GCAES plant is able to provide one or more of the full rangeof shorter duration ancillary services to the grid concurrently with thefulfillment of a long-duration power service. A GCAES plant may alsoprovide only ancillary services, only long-duration power services, orany combination of the foregoing. With respect to the provision ofancillary services, the GCAES system enables enhanced amplitude ofincreases and decreases in the amount of power provided, as well asfaster ramp rates up and down, and more frequent repeatability of up anddown ramping, than is present in existing systems.

Ancillary services are means of providing electric power to the grid inways that meet particular needs that are a function of unpredictable andstochastic aspects of the power market, e.g., unpredictable variationsin demand as end-users vary their usage during the course of each day,and unpredictable variations in supply such as outages of generatorunits and variations in the amount of power supplied by intermittentsources. Ancillary services are often characterized as response andreserve. Such services are typically characterized in categories thatproceed from shortest response timeframes to longer response timeframes.Currently it is customary to refer to three basic categories of responseand reserve, or ancillary services, the nomenclature and metrics ofwhich are partially variable depending on the region, country, orRegional Transmission Organization (RTO) in question, while sharingbasic characteristics.

One type of ancillary service that a GCAES plant is able to provide,while simultaneously fulfilling a long-duration power service, isfrequency response, sometimes called primary reserve. To provide thisservice, the GCAES plant reacts to momentary drops and increases insystem frequency (e.g., variations from 60 Hz in United States or 50 Hzin European systems), increases or decreases the amount of powersupplied to the grid within timeframes of seconds (or potentiallyfractions of a second), and maintains such response for a designatedperiod of time, which may be as short as 30 seconds in some instances,or may be defined as a number of minutes.

GCAES plants are also capable of providing spinning reserves, sometimescalled secondary reserves, which requires the plant to respond within atimeframe set by the duration of the primary reserve or frequencyresponse. For example, if frequency response ancillary services arerequired by the RTO to provide a duration of at least 30 seconds, thensecondary reserves or spinning reserves must be able to react within atmost 30 seconds. An example in the United States is the CaliforniaIndependent System Operator (ISO), which requires spinning reserves tobe able to increase power output within 60 seconds after the ISOdetermines that power from spinning reserves needs to be dispatched; theCalifornia ISO requires similar response times for non-spinning reservesto decrease power production or increase demand, requiring that theamount of additional load be at least 1 MW and capable of a duration ofat least two hours. Utilizing its storage and generation capabilities,the GCAES system is able to meet various load and duration demands whilefulfilling, for example, a baseload or intermediate contract at the sametime.

Tertiary reserves include ancillary services denominated as replacementreserves, standing reserves, contingency reserves, response reserves, orsynchronized reserves, and provide a response within the timeframe setby the duration of secondary reserves, which will typically be atimeframe defined in terms of minutes or one or two hours. Tertiaryreserves must be maintainable for a long duration. GCAES plants are alsocapable of meeting these response and duration requirements forproviding tertiary reserves.

In addition to providing ancillary services such as load following,frequency regulation, spinning reserve, non-spinning reserve, blackstart, and ramp-rate control, GCAES plants can provide reactive powercontrol to assist in controlling voltage levels throughout an electricalsystem. GCAES plants can further provide load source on demand response,in which a source of energy is needed to absorb energy from a powergrid, effectively acting as an energy sink. Under this circumstance, aGCAES plant could convert the energy and transfer it to storage forlater use. The GCAES system can further provide ancillary servicesdemand response to ensure proper operation of a transmission grid.

Providers of ancillary services must typically have a minimum ratedgenerating capacity, such as 1 MW, and must typically satisfy standardsfor communication and control, such as ability to respond to ISOdirection and control, including dispatch instructions, without humanintermediation. Prospective providers of ancillary services typicallyare required to apply to the RTO/ISO for approval and certification toprovide such services. In addition to ancillary services, RTO/ISOsestablish and operate markets for baseload power on a day-ahead andlonger term basis, as well as intermediate or following load power.GCAES plants meeting regional capacity and other requirements are ableto take advantage of these ancillary service and long-duration powerservice markets.

If a power source is not meeting current needs (e.g., if the powersource is a wind farm, and there is insufficient wind), a GCAES plant isstill able to fulfill a baseload power purchase agreement by using theenergy that is available from the power source, in combination withenergy obtained from storage. If the storage capacity is sufficientlylarge, it may contain enough stored energy (e.g., compressed air) tofulfill baseload for an extended period of time in the above-describedcircumstances. In the case of smaller storage units, supplying energyvia this combination of sources may not be feasible beyond a limitedperiod; as such, energy trading may play a larger part in fulfilling thebaseload contract.

Power generation using the GCAES system also negates the risk that thewrong type of power plant will be built. The overall system has at leastthree elemental aspects whose relative size may affect important powerperformance characteristics : the power source (e.g., wind turbines),cavern capacity, and the GCAES equipment. Each element may be sized tomeet the energy needs of a customer; i.e., the number of wind turbines,GCAES units, or amount of cavern capacity can be adjusted to move withenergy demand and/or the energy market.

For example, if a peaker plant is constructed with the capacity to rampup and down, but later circumstances require additional baseload, thenthe wrong generator has been built and substantial capital expenditurehas been wasted. Conversely, the GCAES system is flexible such that itisn't fixed as a baseload or peaker plant. If, initially, a GCAES plantis built to primarily supply baseload, but the need for peaking laterarises, all that is required is to incorporate additional GCAES unitsand related equipment into the plant, and keep the wind turbines orother intermittent power source the same. Alternatively, if a GCAESpeaker plant is built, and at a later time additional base capacity isrequired, no changes are made to the GCAES equipment, but more windturbines may be added.

Various minimum, maximum, and typical values and ranges for theoperation of GCAES plants and associated systems related to energystorage and delivery are described in FIG. 2. The power source connectedto a GCAES plant may supply 1.5 MW to 2000 MW of power, with a typicalsupply being approximately 100 MW. The storage capacity, namely caverncapacity, utilized by the plant may be between 20 kcf and 4 bcf, withcommon ranges falling around 1 billion cubic feet. Gas compressed by theGCAES system is stored in the storage subsystem at 70 to 95 Bar, butpressures may range from approximately 20 to 200 Bar. GCAES unitscompress gas in two stages: in the first stage, gas is compressed to 1-7Bar, while in the second, gas is compressed to 7-90. Expansion is alsoperformed in a two-stage process at substantially similar pressures. TheGCAES units may, however, compress gas at pressures ranging from 5 Barto 200 Bar utilizing a process with a varying number of stages.

GCAES units have a rapid response rate when switching modes. Alternatingbetween storage and generation modes can generally be accomplished in0.25 to 4.2 seconds, with the switch occurring in as little as 50 ms inoptimal conditions. Switching from an idle mode to either storage orgeneration can also be accomplished in approximately 0.25 to 4.2seconds, with a floor of 50 ms for optimal conditions.

Power plant elements are sized with regard to the energy performancerequired to meet predictable customer demands. In addition, a GCAESplant's elements may also be sized to include additional capacity thatallows the plant to participate in electricity market power-trading.Power plant element sizing may involve the relative sizing of, e.g.,additional wind turbines or GCAES units or storage volume. Moreover, theneed for additional equipment needed to participate in power-trading maybe minimal, or even none, because the need may be considered withrespect to the economic effects of weather and other factors that areforecast rather than deterministically known. Further, the need foradditional equipment or storage capacity may recognize that theequipment that supports long-term power contract(s) can also supportshort-term power-trading, and therefore enable the operator to benefitfrom understanding short-term energy price, supply, and demand, with orwithout investing in power-trading dedicated equipment.

The power trading component incorporated in the GCAES system improvesupon existing methods and systems for creating and clearing a market forelectric power, by enabling wind-power and other intermittent renewablepower sources to participate at full market value, with enhanced profitand return on investment, thus boosting the development of renewableenergy in the competitive electric power markets of the United Statesand other regions of the world.

It should be noted that this system for GCAES-based power trading can bepracticed in combination with a wind farm or other intermittent energysource, or solely utilizing power obtained from the grid, or acombination thereof; and can be practiced with or without a contract tosupply long duration power. This system can be employed not only toreduce power output to the grid, but also to accept load from the grid.The GCAES system therefore is able to function simultaneously orseparately in various modes; for example, the system can providelong-duration power services and/or ancillary power services, as well asengage in power trading to fulfill services and/or convert energyto/from storage. The GCAES system can operate in any one of these modesor any combination thereof. In some instances, the system may provideboth long-duration and ancillary power services. In other circumstances,for example, the system may provide ancillary services while engaging inpower trading.

As part of the power trading component, market conditions are analyzedin time increments, preferably very short increments, from 30 seconds toan hour, or any other suitable time period. If, during that increment,the market price of power is below a particular threshold, such as ahistorical average, daily average, 24-hour rolling average, or someother indicator, that power can be purchased, and idle GCAES equipmentcan be used to put the energy into storage. Further, if the market priceis below the price of a baseload contract, the cheaper power can be usedto fulfill the contract for that time increment. In other words, thepower can be purchased at the low market price and sold at the contractprice directly through market trading—no interaction with the GCAESconversion system is necessary. Along the same lines, if the marketprice of power is above a particular threshold, and the GCAES equipmentis not currently in use to supply power for the firm power contract(s),the GCAES plant can release energy from storage and supply it to thegrid at the market price.

In some embodiments, one or more market factors may be used in makingtrading decisions, such as whether to buy or offer to buy power, andwhether to sell or offer to sell power, as well how much power and atwhat price. The market factor may be, for example, a past market priceof power, present market price of power, future market price of power,trending price of power, average price of power defined over a fixedtimeframe, average price of power defined over a variable timeframe,supply of power, demand of power, supply trend, demand trend, or anyhistorical or predictive value of the foregoing. The market factor mayinclude a single value, multiple values, and/or ranges of values.

In a more specific example, if a GCAES plant with 200 MW of windturbines has obligations to supply power under a 100 Megawattintermediate contract at $70 per Megawatt-hour, and the wind is blowingat half-power during off-peak hours, there are several possible actionsthat can be taken depending on market conditions. If, for instance,power spot prices are well below the average price and the contractprice (e.g., the spot price is $5/MW·h), and not all GCAES units in theplant are being utilized, then it is advantageous to purchase power andcompress to storage, to the full extent of available GCAES equipment andstorage capacity, for that time increment. In the opposite example, ifit is daytime (when power must be supplied under contract), the windturbines are producing 200 MW, and the price of power on the spot marketis $200/MW·h, then the plant can take advantage of these conditions innumerous ways. First, 100 MW has to be supplied under contract at$70/MW·h. If possible, the extra 100 MW from the wind turbines can thenbe sold on the spot market for $200/MW·h (i.e., the extra 100 MW isrouted from the wind turbines to the grid, bypassing the GCAESconversion and storage equipment). Going even further, because the GCAESunits will likely be idle (no compression is necessary), the units canbe put into expansion mode to sell stored energy for that time/increment. That is, if 100 MW of stored energy was initially purchasedat $5/MW·h, it can then be sold at the $200 spot market price. In theseconditions, therefore, a GCAES plant set up to satisfy a 100 MW supplycontract can actually supply 300 MW, with potentially substantial profitderived from supplying the extra 200 MW.

Referring to FIGS. 3A-3C, the tables represent examples of how energyfrom a power source and storage may be combined with trading to satisfya baseload contract. The “Power Source (MW)” column indicates how muchpower is received from the power source per time unit, in MW. The “GCAES(MW)” column indicates how much power is transmitted through the GCAESunit per time unit, in MW, with a positive number designating expansionof energy from storage, and a negative number designating compression ofenergy to storage. The “Grid (MW)” column indicates how much power istransmitted to the grid per time unit, in MW. In each of FIGS. 3A-3C,the following exemplary limitations are assumed. First, desired outputto the grid is at least 100 MW, to fulfill a 100 MW baseload contract.Second, the GCAES plant is capable of converting a maximum of 100 MW pertime unit.

FIG. 3A describes an exemplary baseline energy balance case in which notrading is used to satisfy the baseload contract. In the first row, highwind conditions result in excess power output of 100 MW, which isconverted by the GCAES system into compressed gas storage. The remaining100 MW is supplied directly to the grid, avoiding any efficiency lossesassociated with the energy storage system. The second row shows the casein which the power source exactly meets the baseload requirement; thus,the full 100 MW is directed from the power source to the grid. The thirdrow displays the situation in which the power source is supplying noenergy, and the full 100 MW is expanded from stored gas by the GCAESunit.

FIG. 3B expands upon the baseline case by factoring in energy-sellingwhen market prices surpass a threshold above the average. In this case,it is advantageous to retrieve stored energy and supply it to the grid.As such, the GCAES equipment will provide its maximum of 100 MW incombination with the amount of power that is received from the powersource. Thus, for each wind intensity, the total power supplied to thegrid is the amount received from the power source plus 100 MW.

Referring to FIG. 3C, when market prices fall under a threshold that isbelow the average, it becomes desirable to purchase and store energy forlater sale when market prices rise. As shown on the table, the GCAESequipment will compress and store a maximum of 100 MW. In the high-windcase, 100 MW is supplied to the grid to meet the baseload contract, and100 MW is stored. In the average-wind case, the 100 MW from the powersource can be used to fulfill the baseload contract, or it can beconverted to storage. If stored, the baseload contract can be fulfilledby buying power from the market at the lower price and selling at thehigher, contracted price. If used to directly fulfill the contract, then100 MW will be purchased at the low price and converted to storage. Inthe case where no wind is blowing, the table shows that 200 MW of energyis purchased at the low market price: 100 MW is supplied under thebaseload contract, and 100 MW is converted to storage. It should benoted that in certain circumstances, it may be preferable to satisfy thebaseload contract partially or entirely through expansion of storedenergy; however, that situation is not addressed in FIG. 3C. Further,power purchasing alone can be used to satisfy a baseload contract.

In other cases, market prices, equipment availability, overhead costs,and other factors may cause variations in these values. For example,certain circumstances may result in a situation where it is desirable toprovide power to the grid from any combination of the power source,storage, and energy market sales. Similarly, energy for storage can beobtained by any combination of the power source and energy marketpurchases.

It should be noted that the tables provided in FIGS. 3A-3C are examplesof the basic operation of the inventive subject matter, and, as such,the values used are for purposes of illustration and may not reflectactual values existing in the system. Further, the situations describedmay be oversimplified to illustrate basic concepts of the system andtherefore do not represent all possible circumstances, results, andconsiderations that may be taken into account when operating the system.

At its core, the trading aspect of the system comprises three tradingrules to address three issues: First, when should energy be traded?Second, how much energy should be traded? And third, how does storageaffect trading?

Rule number one states that power should be bought or sold when it isincrementally profitable to do so. For example, if “profitable” isdefined in relation to an average price of power, whether for an hour, aday, a rolling 24-hour period, a week, a month, a year, or some othertime period, then power will be bought when the spot market price (orother market factor) is less than the average price by a thresholdamount Likewise, power will be sold when the spot market price (or othermarket factor) is greater than the average price by a threshold amount.The buy threshold amount may or may not be the same as the sellthreshold amount.

Some embodiments of the trading systems and methods described herein donot require any predictions about market or environmental conditions tobe made to accomplish the goal of the invention. In some cases, anenergy trade is made if it is incrementally profitable at the presenttime, and no waiting occurs to determine if a later time increment maybe more or less profitable. In an exemplary estimation, to beincrementally profitable, power must be purchased at 20% below theaverage market price. This percentage is derived primarily from theefficiency loss of the GCAES device, which is about 86 to 87% efficientin compression mode, plus the operating costs of the equipment, whichmay vary, but for purposes of illustration is $2.50/MW·h. In addition,trading costs must be factored into the equation. To sell powerprofitably, it must be sold at a similar rate above the average price,or 20% as herein described. These percentage thresholds may varydepending on equipment efficiency, operating costs, trading costs, andother factors.

Certain trading costs that may be factored into the calculation of thebuy and sell thresholds include power price modifications made byelectricity spot market controllers. One example of such controllers areRegional Transmission Organizations (RTOs), which are the primary spotmarkets for electricity in the U.S. and many other parts of the world.The RTO spot market process is based on generators of electricitysupplying an offer price, and on loads (the distributors of electricpower to end-users) offering a bid price, to buy electricity. The offersand bids are placed, for example, every five minutes with the RTO.Subsequently, the RTO sets a price and sends instructions (dispatch) tothe generators specifying how much electricity they are to supply to thegrid and the price they will be paid for the electricity. The spotmarket prices (called Location Marginal Pricing or LMP) are set based onthe bids and offers, reserve requirements, transmission congestion,location of the demand and supply and a number of other factors. The RTOhas the authority to change the offers from the generators and use thechanged offering in calculating the LMP. Often, the generator does nothave the ability to reject the price specified by the RTO or to decidehow much electricity or reserve will be supplied to the grid. Taking allthis into account, the system may consider the RTO's abilities to setelectricity prices, as well as the existence of other bids and offers,demand and supplies, and other factors relating to the calculation ofthe LMP, in making bids and offers to a spot market controller. Theforegoing factors may further be considered by the GCAES system indetermining how much power to buy or sell, or offer to buy or sell, aswell as how much energy to store or retrieve from storage.

Referring to FIG. 4A, an exemplary graph shows the market price ofelectricity over time. The average market price is represented as auniformly-dashed line, with the sell threshold being some amount abovethe average market price (e.g., 20% above), and the buy threshold beingthe same or a different amount below the average market price (e.g., 20%below). Based on the market price over time, power will be sold betweentimes T₀ and T₁, when the price is above the sell threshold (assumingstorage supply exists). Likewise, power will be purchased between timesT₂ and T₃, when the price is below the buy threshold (assuming storagecapacity exists).

Rule number two specifies that the full capacity available in that timetrading period should be bought or sold; however, this amount may varybased on other conditions. The amount of energy that can be processedduring the time increment is dependent on the availability andcapability of a plant's GCAES equipment. Without looking ahead to latertime increments, the full power capacity capable of being processed bythe GCAES units is traded, preferably without regard to energy storage.Comparing the power plant to a car, the GCAES units can be consideredthe engine, and the storage as the gas tank. Under Rule Two, the primaryconcern is how much the engine can be utilized over the next timeincrement, without regard to the contents of the gas tank.

Rule number three indicates that available storage capacity should betaken into account when making trading decisions. With regard to theexemplary 20% above-20% below average price band discussed above, this40% pricing band should be slid up and down depending on how fullstorage is. In some cases, both band boundaries slide at an equivalentrate, while in other cases, the boundaries may move independently. As anexample, if the energy storage vessel is 95% full, the trading modelshould represent one in which selling is preferable over buying. To thateffect, for the time increment during which storage capacity is at this95% level, the 40% pricing band should be moved down such that powerwill be sold closer to the average price, at the average price, or evenbelow the average price, in order to avoid filling or over-filling thestorage tank. At the other end of the band, power will not be purchasedunless it is far below the average price, e.g., about 40% below orlower. Conversely, when the storage tank approaches empty, the pricingband is shifted up so that buying power is preferable over selling. Forexample, rather than buying/selling at 20% below/above the average,power purchases will be made at 10% below the average and sold at 30%above. Using this method of trading, the system is freed from having topredict future environmental or marketing conditions and the risksinherent therewith.

Referring to FIG. 4B, as storage approaches full, the sell/buythresholds slide downward, causing power to be sold at lower prices(i.e., between T₀ and T₁), and purchased at lower prices than those inthe FIG. 4A baseline case, assuming the average market price is constantamong FIGS. 4A-C. As shown in FIG. 4B, the buy threshold has droppedbelow the lowest market price, resulting in no power purchases.

Conversely, in FIG. 4C, as storage approaches empty, the sell/buythresholds shift upward, causing power to be sold at higher prices, andpurchased at higher prices (i.e., between T₀ and T₁) than those in theFIG. 4A baseline case, assuming the average market price is constantamong FIGS. 4A-C. As shown in FIG. 4C, the sell threshold has risenabove the highest market price, resulting in no power sales.

In some embodiments a fourth rule is included, which states that theavailability rating required in a power purchase agreement (PPA) may bealtered to produce more favorable trading outcomes. The availabilityrating in a PPA is the percentage of time that the system is availableto generate power. For example, nuclear plants and coal plants generallyhave a 90% availability, with nuclear slightly higher and coal slightlylower. To avoid inconveniencing customers, these plants will performservicing mostly in the spring and fall, when loads are lowest. GCAESplants are modular and do not normally require the entire plant to bebrought down for servicing. Further, some GCAES plants may have extraGCAES units installed, thus allowing for the swapping in and out ofunits for maintenance, resulting in no noticeable effect on the plant'scapacity to generate power.

There are at least two separate ways in which a PPA can be incorporatedinto trading logic. First, trading may be used to avoid failure inmeeting a PPA. For instance, if there is insufficient power beinggenerated from the intermittent power source over a long period of time,then the trading algorithm will ensure that power is purchased to fillthe storage tanks, and availability under the PPA will subsequentlyrise. Conversely, if the power source is supplying an overabundance ofenergy, and storage is nearly full, the trading algorithm will shift thepricing band as necessary so that more power is sold. By selling thepower and maintaining sufficient storage capacity, excess energy is notwasted, and the PPA can be satisfied at later dates, even if the sourceof power decreases in its generation capacity.

The second way in which a PPA and energy trading interact involvestrading around the PPA. For purposes of illustration, consider a GCAESplant having a baseload contract at $70/MW·h, with a 90% availabilityrequirement. In one example, if gas prices rise, causing spot andpeaking power prices to go up to $110/MW·h, a trader will be incented tomeet the 90% availability target at $70/MW·h, and sell the remainingavailable power output at $110/MW·h. More generally, if power prices arehigh, it is desirable to meet only the minimum availability requirementsunder a PPA. If, on the other hand, gas prices fall drastically, causingspot and peaking prices to decrease to $40/MW·h, it may be preferable toexceed the required minimum availability under the PPA (i.e., sell underthe contract at $70/MW·h), especially if market prices are not expectedto rise to the PPA contract price. Thus, this second method allowsflexibility in meeting availability under a PPA in response to marketconditions, while at the same time ensuring the fulfillment of long-termpower supply contracts.

Various minimum, maximum, and typical values and ranges for theabove-described fixed-band energy trading systems and methods aredescribed in FIG. 5. In a typical scenario, the sell and buy margins areset at predetermined amounts above and below an average market price ofelectricity, or other factor. Based on the amount of storage capacityavailable, the margins may be shifted up or down by a certain amount.The full capability of energy storage or generation of the GCAES plant,GCAES unit or units (or other amount of energy) is traded per a set timeinterval when the current market price, or other factor, falls outsideof the sell/buy margins.

In some embodiments, predictive elements are incorporated into thedetermination of whether to buy/sell and compress/expand energy.Referring to FIG. 6, an optimization model may use, for example,environmental forecasts (e.g., expected wind power, temperature,pressure, humidity), market conditions predictions (e.g., future price,demand), or other future factors in optimizing energy storage anddelivery. Considering the available inputs as a whole, the optimizationmodel determines the most advantageous configuration in differentcategories to maximize internal rate of return (IRR) and long-term netpresent value (NPV).

Aside from the predictive aspects, the three main categories preferablyconsidered in the optimization model are the physical configuration of aproject, the different approaches for operation of the project, and themarket participation. The model evaluates the physical capabilities of aplant, which may include, for example, the size and number of windturbines, the capabilities of the GCAES units available, the size of thestorage cavern, and the ability to recapture heat. Examples of operationoptimization include a dispatch algorithm, discussed in further detailbelow, and deciding, for example, whether to run 50% of the GCAES unitsat 100% capacity or 100% of units at 50% capacity. In the last category,the model decides, based on the specific region, how and in whichpotential markets the plant should participate.

FIG. 7 is an exemplary diagram of the inputs that may be incorporatedinto the dispatch algorithm, as well as the possible outputs thereof.The dispatch algorithm may be a module of the optimization system usedto optimize the energy dispatch operation of the plant. First, thealgorithm is initialized using a set of configuration parameters (e.g.,storage capacity, starting inventory, compression cost, expansion cost,number of GCAES units, maximum wind farm output, percentage expansionloss, percentage compression loss, maximum hourly compression per unit,maximum hourly expansion per unit). Following initialization, at thebeginning of a time interval based on the region (e.g., five minutes,thirty minutes, one hour, or any other period based on the regionalmarket), the algorithm considers the actual storage level, forecastedprice, and wind data, for a predictive time period (e.g., 24 hours, 168hours, or any suitable time period), and runs the optimizationmethodology to come up with the optimal solution for both the operationroom and the trading room for the current time interval. Specifically,the algorithm outputs the amount of energy that should be compressed orexpanded, as well as how much power should be bought or sold during theinterval to maximize total revenue. This process or portions thereof maybe repeated at the beginning of each time interval to maximize revenuewhile satisfying the constraints such as keeping the storage levelwithin its minimum and maximum capacity at all times.

Referring to FIG. 8, a sample result of running the optimization systemand its accompanying algorithmic modules is shown over a 24-hour period,with time intervals of one hour. The graph illustrates the satisfactionof a 100 MW·h power purchase agreement, while simultaneously maximizingrevenue by buying at lower prices and selling at higher prices. Thealgorithm considers both the price and wind factors to decide how muchto compress/expand and buy/sell at a given time.

Various minimum, maximum, and typical values and ranges for theabove-described predictive energy trading systems and methods aredescribed in FIG. 9. In evaluating whether energy is to be stored,generated, and/or traded, the system may account for current contractprices (e.g., baseload or other long-duration, or ancillary servicecontract), the market price of energy (past, present and/or future), thesupply and/or demand of electricity (past, present, and/or future), andvarious past, present or future environmental conditions, including butnot limited to wind speed, wind direction, air temperature, airpressure, humidity, precipitation, cloud cover, season, length ofdaylight, tidal status, storage temperature, storage time, storagepressure, and day/night temperature differential.

In some embodiments, the invention incorporates one or more computercontroller devices for facilitating various operations of the system.For example, computing devices may facilitate the operation of powerrouting subsystems and power conversion subsystems separately or incombination with each other or a number of other subsystems.Instructions may be implemented on the computing devices such that thepower routing subsystem is automatically directed to transfer energyfrom a power source to a power grid. Further, the computing devices mayinclude instructions for automatically directing the conversionsubsystem to store or generate power. The computing devices may directthese subsystems to operate such that power is both directed to the gridand either converted to or from storage simultaneously. Moreover, anynumber of inputs may be considered by the computing devices indetermining how the system and its various subcomponents should operate.For example, the computing devices may evaluate the current operatingconditions of a GCAES plant, storage capacity, present, past and/orenvironmental conditions, market conditions, and make determinations onhow the system should operate to meet present and future power demands.

The computer controller may be implemented on such hardware as a smartor dumb terminal, network computer, workstation, minicomputer, mainframecomputer, or other computing device that is operated as a generalpurpose computer or a special purpose hardware device. Referring to FIG.10, the controller may include a computing device in the form of acomputer 1000 including a processing unit 1002, a system memory 1004,input and output devices 1008, and a system bus that couples varioussystem components including the system memory to the processing unit.

In some embodiments, the controller includes controller software forautomatically directing the operation of the system and/or permitting auser to interface with the system and its various subcomponents. Thecontroller software may be in the form of a standalone application,implemented in a multi-platform language/framework such as Java, .Net,Objective C, or in native processor executable code. Any suitableprogramming language may be used in accordance with the variousembodiments of the invention. Illustratively, a programming languageused may include assembly language, Ada, APL, Basic, C, C++, C#,Objective C, COBOL, dBase, Forth, FORTRAN, Java, Modula-2, Pascal,Prolog, REXX, and/or JavaScript, for example. Further, it is notnecessary that a single type of instruction or programming language beutilized in conjunction with the operation of the system and method ofthe invention. Rather, any number of different programming languages maybe utilized as is necessary or desirable.

In one embodiment, a communications network 1010 connects the computer1000 with other systems and devices, such as remote system controllersand power market servers. The communication may take place via any mediasuch as standard telephone lines, LAN or WAN links (e.g., T1, T3, 56 kb,X.25), broadband connections (ISDN, Frame Relay, ATM), wireless links(802.11, bluetooth, GSM, CDMA, etc.), and so on. The type of network isnot a limitation, however, and any suitable network may be used.Non-limiting examples of networks that can serve as or be part of thecommunications network 1010 include a wireless or wired Ethernet-basedintranet, a local or wide-area network (LAN or WAN), and/or the globalcommunications network known as the Internet, which may accommodate manydifferent communications media and protocols. When used in a LANnetworking environment, computers may be connected to the LAN through anetwork interface or adapter. When used in a WAN networking environment,computers typically include a modem or other communication mechanism.Modems may be internal or external, and may be connected to the systembus via the user-input interface, to the network via wireless or wiredEthernet, or other appropriate mechanism. Computers may be connectedover the Internet, an Intranet, Extranet, Ethernet, or any other systemthat provides communications. Some suitable communications protocols mayinclude TCP/IP, UDP, or OSI for example. For wireless communications,communications protocols may include Bluetooth, Zigbee, IrDa or othersuitable protocol. Furthermore, components of the system may communicatethrough a combination of wired or wireless paths.

The invention may also be practiced in distributed computingenvironments where tasks are performed by remote processing devices thatare linked through a communications network. In a distributed computingenvironment, program modules may be located in both local and remotecomputer storage media including memory storage devices.

In some cases, relational (or other structured) databases may providesuch functionality, for example as a database management system whichstores data related to the operation of the system. Examples ofdatabases include the MySQL Database Server or ORACLE Database Serveroffered by ORACLE Corp. of Redwood Shores, CA, the PostgreSQL DatabaseServer by the PostgreSQL Global Development Group of Berkeley, CA, orthe DB2 Database Server offered by IBM.

Computers typically include a variety of computer readable media thatcan form part of the system memory and be read by the processing unit.By way of example, and not limitation, computer readable media maycomprise computer storage media and communication media. The systemmemory may include computer storage media in the form of volatile and/ornonvolatile memory such as read only memory (ROM) and random accessmemory (RAM). A basic input/output system (BIOS), containing the basicroutines that help to transfer information between elements, such asduring start-up, is typically stored in ROM. RAM typically contains dataand/or program modules that are immediately accessible to and/orpresently being operated on by processing unit. The data or programmodules may include an operating system, application programs, otherprogram modules, and program data.

The computing environment may also include otherremovable/non-removable, volatile/nonvolatile computer storage media.For example, a hard disk drive may read or write to non-removable,nonvolatile magnetic media. A magnetic disk drive may read from orwrites to a removable, nonvolatile magnetic disk, and an optical diskdrive may read from or write to a removable, nonvolatile optical disksuch as a CD-ROM or other optical media. Other removable/non-removable,volatile/nonvolatile computer storage media that can be used in theexemplary operating environment include, but are not limited to,magnetic tape cassettes, flash memory cards, digital versatile disks,digital video tape, solid state RAM, solid state ROM, and the like. Thestorage media are typically connected to the system bus through aremovable or non-removable memory interface.

At a minimum, the memory includes at least one set of instructions thatis either permanently or temporarily stored. The processor executes theinstructions that are stored in order to process data. The set ofinstructions may include various instructions that perform a particulartask or tasks. Such a set of instructions for performing a particulartask may be characterized as a program, software program, software,engine, module, component, mechanism, or tool.

The system may include a plurality of software processing modules storedin a memory as described above and executed on a processor in the mannerdescribed herein. The program modules may be in the form of any suitableprogramming language, which is converted to machine language or objectcode to allow the processor or processors to read the instructions. Thatis, written lines of programming code or source code, in a particularprogramming language, may be converted to machine language using acompiler, assembler, or interpreter. The machine language may be binarycoded machine instructions specific to a particular computer.

The processing unit that executes commands and instructions may be ageneral purpose computer, but may utilize any of a wide variety of othertechnologies including a special purpose computer, a microcomputer,mini-computer, mainframe computer, programmed micro-processor,micro-controller, peripheral integrated circuit element, a CSIC(Customer Specific Integrated Circuit), ASIC (Application SpecificIntegrated Circuit), a logic circuit, a digital signal processor, aprogrammable logic device such as an FPGA (Field Programmable GateArray), PLD (Programmable Logic Device), PLA (Programmable Logic Array),RFID integrated circuits, smart chip, or any other device or arrangementof devices that is capable of implementing the steps of the processes ofthe invention.

It should be appreciated that the processors and/or memories of thecomputer system need not be physically in the same location. Each of theprocessors and each of the memories used by the computer system may bein geographically distinct locations and be connected so as tocommunicate with each other in any suitable manner. Additionally, it isappreciated that each of the processor and/or memory may be composed ofdifferent physical pieces of equipment.

A user may enter commands and information into the computer 1000 througha user interface that includes input devices 1008 such as a keyboard andpointing device, commonly referred to as a mouse, trackball or touchpad. Other input devices may include a microphone, joystick, game pad,satellite dish, scanner, voice recognition device, keyboard, touchscreen, toggle switch, pushbutton, or the like. These and other inputdevices are often connected to the processing unit through a user inputinterface that is coupled to the system bus, but may be connected byother interface and bus structures, such as a parallel port, game portor a universal serial bus (USB).

One or more monitors or display devices may also be connected to thesystem bus via an interface. In addition to display devices, computersmay also include other peripheral output devices 1008, which may beconnected through an output peripheral interface. The computersimplementing the invention may operate in a networked environment usinglogical connections to one or more remote computers, the remotecomputers typically including many or all of the elements describedabove.

Although internal components of the computer are not shown, those ofordinary skill in the art will appreciate that such components and theinterconnections are well known. Accordingly, additional detailsconcerning the internal construction of the computer need not bedisclosed in connection with the present invention.

The foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. As will be understood by thoseskilled in the art, the present invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Various steps as described in the figures andspecification may be added or removed from the processes describedherein, and the steps described may be performed in an alternativeorder, consistent with the spirit of the invention. Accordingly, thedisclosure of the present invention is intended to be illustrative, butnot limiting of the scope of the invention, as well as other claims. Thedisclosure, including any readily discernible variants of the teachingsherein, define, in part, the scope of the foregoing claim terminology.

1-20. (canceled)
 21. An energy storage and delivery system comprising: afirst connection for connection to a power source; a second connectionfor connection to an energy storage subsystem; a third connection forconnection to a power grid; a power trading subsystem for buying powerfrom and selling power to a power trading market; and a controlsubsystem for directing, based at least in part on a market factor, theenergy storage and delivery system to utilize power available from thepower source, the energy storage subsystem, and the power tradingsubsystem to fulfill a power service requirement.
 22. The system ofclaim 21, wherein the power source comprises an intermittent powersource selected from the group consisting of wind energy, solar energy,wave energy, tidal energy, falling water, hydro energy, biomass energy,and geothermal energy.
 23. The system of claim 21, wherein the energystorage subsystem comprises a storage medium selected from the groupconsisting of fluidic storage, mechanical storage, kinetic storage,electrical storage, electrochemical storage, and thermal storage. 24.The system of claim 21, wherein the energy storage subsystem comprises astorage volume in a form selected from the group consisting of apressure vessel, a subterranean cavern, a well, a flywheel, a battery,piping, a bladder, a hydrostatically pressure-compensated container, alake, a pond, a liquid storage vessel, a water retention structure, anda capacitor.
 25. The system of claim 21, wherein the power tradingsubsystem is adapted to initiate at least one of a purchase ofelectricity, an offer to purchase electricity, a sale of electricity,and an offer to sell electricity.
 26. The system of claim 21, whereindirecting the energy storage and delivery system to utilize powercomprises comparing the market factor to a first threshold selected fromthe group consisting of a present supply, a future supply, a presentdemand, a future demand, an average market price, and a present marketprice.
 27. The system of claim 26, wherein directing the energy storageand delivery system to utilize power further comprises comparing themarket factor to a second threshold determined based on the firstthreshold and an available capacity of the energy storage subsystem. 28.The system of claim 21, wherein the directing step is further based atleast in part on environmental conditions selected from the groupconsisting of present local environmental conditions, projected localenvironmental conditions, present remote environmental conditions, andprojected remote environmental conditions.
 29. The system of claim 21,wherein the directing step is further based at least in part onenvironmental conditions selected from the group consisting of windspeed, wind direction, air temperature, air pressure, humidity,precipitation, cloud cover, season, length of daylight, tidal status,storage temperature, storage time, storage pressure, and day/nighttemperature differential.
 30. The system of claim 21, wherein the marketfactor is selected from the group consisting of a market price ofelectricity, a present market price of electricity, a future marketprice of electricity, a trending price of electricity, a supply ofelectricity, and a demand of electricity.
 31. The system of claim 21,wherein the power service requirement is selected from the groupconsisting of baseload, intermediate, peaking, load following, frequencyregulation, spinning reserve, non-spinning reserve, black start,reactive power control, load source on demand response, and ramp-ratecontrol.
 32. The system of claim 21, wherein the control subsystem isadapted to fulfill a long-duration power service simultaneously with atleast one ancillary power service.
 33. The system of claim 21, whereinthe control subsystem is adapted to fulfill the power service bysimultaneously transferring energy from the power source to the powergrid and one of: (a) converting energy to compressed gas for transfer tothe energy storage subsystem and (b) converting compressed gas to energyfor transfer to the power grid.
 34. The system of claim 21, furthercomprising a power routing subsystem coupled to the power source and thepower grid, and adapted to transfer energy from the power source to thepower grid.
 35. The system of claim 34, further comprising a conversionsubsystem coupled to the power routing subsystem and the energy storagesubsystem, and adapted to convert between energy and compressed gas. 36.The system of claim 35, wherein the conversion subsystem is switchablein substantially real-time between: (a) transferring energy from thepower source or power grid via the power routing subsystem to the energystorage subsystem and (b) transferring energy from the energy storagesubsystem to the power routing subsystem for delivery to the power grid.37. An energy storage and delivery method comprising: connecting to apower source; connecting to an energy storage subsystem; connecting to apower grid; trading energy by at least one of buying power from andselling power to a power trading market; and selectively utilizing,based at least in part on a market factor, power available from thepower source, the energy storage subsystem, and the energy trading tofulfill a power service requirement.
 38. The method of claim 37, whereinthe power source comprises an intermittent power source selected fromthe group consisting of wind energy, solar energy, wave energy, tidalenergy, falling water, hydro energy, biomass energy, and geothermalenergy.
 39. The method of claim 37, wherein the energy storage subsystemcomprises a storage medium selected from the group consisting of fluidicstorage, mechanical storage, kinetic storage, electrical storage,electrochemical storage, and thermal storage.
 40. The method of claim37, wherein the energy storage subsystem comprises a storage volume in aform selected from the group consisting of a pressure vessel, asubterranean cavern, a well, a flywheel, a battery, piping, a bladder, ahydrostatically pressure-compensated container, a lake, a pond, a liquidstorage vessel, a water retention structure, and a capacitor.
 41. Themethod of claim 37, wherein trading energy step further comprisesinitiating at least one of a purchase of electricity, an offer topurchase electricity, a sale of electricity, and an offer to sellelectricity.
 42. The method of claim 37, wherein the utilizing stepfurther comprises comparing the market factor to a first thresholdselected from the group consisting of a present supply, a future supply,a present demand, a future demand, an average market price, and apresent market price.
 43. The method of claim 42, wherein the utilizingstep further comprises comparing the market factor to a second thresholddetermined based on the first threshold and an available capacity of theenergy storage subsystem.
 44. The method of claim 37, wherein theutilizing step is further based at least in part on environmentalconditions selected from the group consisting of present localenvironmental conditions, projected local environmental conditions,present remote environmental conditions, and projected remoteenvironmental conditions.
 45. The method of claim 37, wherein theutilizing step is further based at least in part on environmentalconditions selected from the group consisting of wind speed, winddirection, air temperature, air pressure, humidity, precipitation, cloudcover, season, length of daylight, tidal status, storage temperature,storage time, storage pressure, and day/night temperature differential.46. The method of claim 37, wherein the market factor is selected fromthe group consisting of a market price of electricity, a present marketprice of electricity, a future market price of electricity, a trendingprice of electricity, a supply of electricity, and a demand ofelectricity.
 47. The method of claim 37, wherein the power servicerequirement is selected from the group consisting of baseload,intermediate, peaking, load following, frequency regulation, spinningreserve, non-spinning reserve, black start, reactive power control, loadsource on demand response, and ramp-rate control.
 48. The method ofclaim 37, further comprising the step of delivering power to the grid tofulfill a long-duration power service simultaneously with at least oneancillary power service.
 49. The method of claim 37, further comprisingthe step of fulfilling the power service requirement by simultaneouslytransferring energy from the power source to the power grid and one of:(a) converting energy to compressed gas for delivery to the energystorage subsystem and (b) converting compressed gas to energy fordelivery to the power grid.
 50. The method of claim 37, furthercomprising the step of transferring energy from the power source to thepower grid.
 51. The method of claim 37, further comprising the step ofconverting between energy and compressed gas.
 52. The method of claim37, further comprising the step of switching in substantially real-timebetween: (a) transferring energy from the power source or power grid tothe energy storage subsystem and (b) transferring energy from the energystorage subsystem to the power grid.